1. Field of the Invention
This invention relates to an image forming apparatus and a unit for use therein, and particularly pertains to an image forming apparatus provided with a unit which is incorporated with at least an expendable component and is reusable by periodically replacing the expendable component, and a unit for use in such an image forming apparatus.
2. Description of the Background Art
Generally, image forming apparatus such as copiers and printers are equipped with a variety of expendable components (or consumable items) which are worn out as they are used. It is required to periodically replace these expendable components with new ones. Heretofore, since expendable components are individually replaced one by one, a serviceperson has to check up and adjust a newly installed expendable component so that the newly installed expendable component is normally operated in addition to a replacing operation, which makes the serviceperson's operation cumbersome and complicated.
In view of the above, recently, an idea has been proposed to simplify a replacing operation by assembling expendable components and peripheral parts in vicinity of the expendable components into a one-piece unit as many as possible and by replacing the expendable components as the unit. This idea is very practical in supporting the reuse activity, which has been promoted recently, because the unit is reusable.
Examples of units which are incorporated with an expendable component or components and which are reusable by periodically replacing the expendable component(s) are a charging unit for charging the surface of a photosensitive drum, a developing unit for adhering toner onto an electrostatic latent image which is formed on the drum surface by an optical section to develop the latent image into a toner image, a transferring unit for transferring the toner image onto a sheet, a cleaning unit for removing toner residuals on the drum surface after the image transferring, and a fixing unit for fixing the transferred toner image onto the sheet.
A discharging wire for charging the drum surface, a developer container containing a developer consisting of toner and carriers, and a discharging wire for attracting a toner image formed on the drum surface onto a sheet are some of the examples of the expendable components in the charging unit, the developing unit, and the transferring unit, respectively. Adhesive members which are attached to axially both ends of a cleaning blade and are rendered in pressing contact with the drum surface, and a pair of heating roller and a pressing roller for fixing a toner image on a sheet while passing the sheet in a clearance defined by the roller pair are some of the examples of the expendable components in the cleaning unit and the fixing unit, respectively. The cleaning blade has a contact area with a length not shorter than the maximum width of a toner image producible on the drum surface.
Each unit has its useful life and does not have durability enough to be usable permanently even if the unit is repeatedly recycled and reused, considering its aged deterioration, stress that has been accumulatively exerted on the unit during its use, or other factor. Continued use of such a unit may adversely affect printing quality and sheet transport performance of the image forming apparatus depending on a record or history on use of the unit such as the number of times of reuse, the period lapsed from start of its use, and the total number of times of use with respect to image forming operation.
In view of the above, there is a strong demand for managing the useful life of each unit when the unit is to be reused by grasping the record or history on its use so that the unit may not be used beyond its useful life. Conventionally, however, there has not been taken a specific measure relating to management of the useful life of each unit. It is often the case that a unit is inadvertently used or reused beyond its useful life, which may lead to unstable performance of the image forming apparatus equipped with such a unit.